Therapeutic agents such as small interfering siRNAs, ribozymes, and anti-sense RNAs show significant potential in new molecular approaches to down-regulate specific gene expression in cancerous or viral- infected cells. The development of safe, efficient, specific and non-pathogenic nano-particles for the packaging and delivery of multifunctional therapeutic RNAs is thus highly desirable. While programmable RNA self-assembly has been shown to potentially provide a solution towards that goal, the underlying principles for the design and engineering of multifunctional nano-structures based on RNA have still to be delineated. The long-term goal of this proposal is to contribute to the development of fully controllable and versatile bio-materials based on RNA and nucleic acid analogs for use in the study of biology, disease diagnosis, or therapy. In order to achieve this challenge, this project aims at generating stimuli-responsive programmable three-dimensional (3D) supra-molecular assemblies with control over their geometry, topology, directionality and addressability and able to respond to the cues of the environment. For instance, programmable, addressable and multifunctional 3D nano-cages that allow precise immobilization in 3D space of various functional therapeutic modules with catalytic or recognition properties will be synthesized and characterized by biochemical and biophysical methods such as AFM and cryo electron microscopy. Some of these RNA nano-devices will be engineered to switch reversibly between distinct supra-molecular shapes in response to small target compounds. The principles underlying the engineering of concerted and transient, time-activated complex functions as well as the enhancement of the chemical stability of these assemblies using RNA structural mimics like locked-in nucleic acid (LNA) will be investigated. This work will provide new insights in the control of self-assembly processes involving large population of RNA molecules and will pave the way towards the design of complex RNA-based nano-machines with strong potential in biology and medicine. It is anticipated that this project will establish the fundamental assembly and functional principles for the design and development of versatile responsive vehicles for therapeutic RNAs that will be suitable for in vivo applications and amenable to industrial-scale development in the future.